The invention is directed to a control apparatus and method to maintain optimum oil-well production while reducing the shock pulses encountered during the pump stroke to an acceptable level without shutting down the oil-well pump.
In many oil-producing formations, after the oil level in the well bore is pumped off, that is, only partially filled, a "pounding" condition is encountered. This condition is caused by the reciprocating pump, i.e., the "walking-beam" unit, stroking faster than the flow of oil to the down-hole pump. This allows an air space to develop between the down-hole pump and the column of oil below it. At the next down stroke, the down-hole pump impacts the oil in the well bore and sends a shock wave up through the polished rod, i.e., the "sucker rod", through the reciprocating oil-well pump assembly including the gearbox. When the pounding is allowed to continue without a pump shut-down, the gearbox and other structural failures subsequently occur.
Various control systems have been suggested to prevent damage to the oil-well pump assembly. One such control assembly is disclosed in U.S. Pat. No. 3,269,320. However, in order to prevent damage to the oil well and oil-well pump assembly, the control system automatically shuts down the oil-well pump and oil production ceases. In U.S. Pat. No. 3,306,210, control means is provided which automatically starts and stops the oil-well pump responsive to the presence of oil in the well bore. In U.S. Pat. No. 3,075,466, an automatic motor-control system is described, whereby the pump is shut off when pounding occurs. Thus, the prior art teaches various control means which prevent damage to the oil well and oil-well pump assembly, simply by sensing the shock pulses encountered in the oil-well bore, or sensing the oil level in the well bore and then shutting the pump down in response thereto, thereby curtailing oil production.